Computed tomography (CT) is an imaging method with which X-ray projections (in this case synonymous with “projections”) are recorded at various different projection angles. In this situation, a recording unit, including an X-ray emitter and an X-ray detector, rotates about an axis of rotation. At the present time, most X-ray detectors of CT devices exhibit several lines along the axis of rotation. They also cover a large area inside the plane of rotation. Due to the fact that X-ray detectors for CT devices are expensive, the intention is that their surface, taking account of performance parameters such as the spatial resolution, should be kept relatively small.
One known possibility for reducing the size of the detector surface is for the detector to be asymmetrical in shape. The reconstruction of images on the basis of X-ray projections which are recorded with such asymmetrical detectors, however, imposes high demands. For the recording of moved structures in particular, such as the beating heart, the demands are particularly high. Specifically, the rotation of the recording unit takes approximately half a second to a second. When recording with an asymmetrical detector, not all the points inside the volume which it is intended should be reconstructed will necessarily contribute to every X-ray projection. Accordingly, for the reconstruction of different points, different X-ray projections must be used, which cover different areas and are therefore temporally skewed.
From the patent application with the application reference DE 102012202499.9, the entire contents of which are hereby incorporated herein by reference, a CT device is known which exhibits a gantry as well as an X-ray source and a detector, wherein the detector exhibits on at least one of its wide sides a side region which exhibits a lesser width than the overall width of the detector, wherein the lateral region, in relation to the overall width of the detector, is arranged offset to the middle. The CT device further exhibits a control apparatus, which, with spiral CT imaging, controls a gantry rotation and a detector advance relative to the volume which is to be imaged, co-ordinated in such a way that a direction of rotation of the gantry rotation and a direction of advance of the detector are matched to one another.